Triplex strand switching

Py Pu Py base triplets as shown in (237). This polanty of binding does not require a special junction such as the 3 -3 linkage previously used between two oligopyrimidine blocks.These results indicate that by using both the known types of base triplets in combination with strand switching the requirement of purely homopurine sequences for triplex formation can be relaxed. 

RR duplexes and the derived triplexes. This could be a consequence of stable duplex structures which need more energy to become distorted to accommodate the third strand. The stability order of various RNA-DNA hybrid triplexes indicates that duplexes with DNA in the purine strand readily bind to either RNA or DNA to form triplexes. In contrast, a purine RNA duplex binds only RNA on a third strand. It was recently shown that RNA cannot be a part of a triplex with the R RY motif [92c]. These studies point to the fundamental role of sugars in controlling nucleic acid recognition through conformational switches. Since RNA-DNA hybrids are cellular targets for a number of... 

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